Spindle motor

ABSTRACT

The spindle motor includes a rotating shaft, a rotor cover which is secured to the rotating shaft and rotates the rotating shaft, a bearing for rotatably supporting the rotating shaft, a holder for holding the bearing, and a holding magnet which is directly mounted to an inner wall of the rotor cover. In this case, the holding magnet is positioned above the bearing to prevent oil from being discharged from the bearing to the outside.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation-In-Part of application Ser. No.11/637,171 filed Dec. 12, 2006, now pending, which claims the benefit ofKorean Patent Application No. 10-2005-0121753, filed on Dec. 12, 2005 inthe Korean Intellectual Property Office, the disclosures of which areincorporated herein by reference.

BACKGROUND

1. Field

The present invention relates generally to spindle motors and, moreparticularly, to a spindle motor, in which the number of parts isreduced, and the yield rate of which is increased.

2. Description of the Related Art

As well known to those skilled in the art, a spindle motor is a devicewhich is mounted on an optical disk drive to drive a turntable, thusrotating a disk mounted on the turntable. Generally, as shown in FIG. 2,a spindle motor 200 includes a rotary unit 201 and a stationary unit205.

The rotary unit 201 is the rotating part of the motor 200, and includesa rotating shaft 211, a rotor cover 221, and a magnet 231.

The rotating shaft 211 functions to rotate a turntable (not shown).

The rotor cover 221 serves to rotate the rotating shaft 211. A shaftfitting hole 222 is formed in the center of the rotor cover 221 so thatthe rotating shaft 211 is fitted into the shaft fitting hole 222. An oildischarge preventing piece 223 is mounted to an end of the shaft fittinghole 222 to prevent oil from being discharged from a bearing 215.Further, the rotor cover 221 extends in a circumferential direction, andan edge of the rotor cover 221 is bent downwards to cover a stator 235.

The magnet 231 forms a magnetic field, and is secured to an inner wall224 of the rotor cover 221.

The stationary unit 205 is the fixed part of the motor 200, and includesthe bearing 215, a holder 225, the stator 235, and a base 245.

The bearing 215 rotatably supports the rotating shaft 211.

The holder 225 holds the bearing 215 to secure the bearing 215 to apredetermined position. The bearing 215 is firmly coupled to the innercircumferential surface of the holder 225.

The stator 235 forms an electric field when external power is applied tothe stator 235. The stator 235 is firmly coupled to the outercircumferential surface of the holder 225.

Further, a holding magnet 236 is coupled to the upper portion of theinner circumferential surface of the stator 235 via a back yoke 237, andholds the disk to prevent the disk from being damaged when the disk (notshown) is rotated.

The base 245 functions to support the entire motor 200. The centralportion of the base 245 extends outwards, thus defining an insertionhole 246. A printed circuit board 247 is mounted on the upper surface ofthe base 245, and controls a signal for driving the motor 200.

However, the conventional spindle motor 200 constructed as describedabove is problematic in that the motor 200 is provided with the backyoke 237 to install the holding magnet 236, and is provided with the oildischarge preventing piece 223 to prevent oil from being discharged fromthe bearing 215 to the outside, so that the number of parts isincreased, the manufacturing process is complicated, and thereby theyield rate is reduced.

SUMMARY

Accordingly, the present invention has been made keeping in mind theabove problems occurring in the prior art, and an object of the presentinvention is to provide a spindle motor, which is constructed so that aholding magnet is directly mounted on a rotor cover, thus reducing thenumber of parts and enhancing the yield rate.

Another object of the present invention is to provide a spindle motor,in which a holding magnet is installed adjacent to the upper portion ofa bearing, thus preventing oil from being discharged from the bearing tothe outside without using an additional part.

In order to accomplish the above objects, the present invention providesa spindle motor, including a rotating shaft, a rotor cover secured tothe rotating shaft by a flange and rotating the rotating shaft, abearing rotatably supporting the rotating shaft, a holder for holdingthe bearing, a stator forming an electric field coupled to the outercircumferential surface of the holder, a holding magnet having arectangular cross section positioned above the bearing, the holdingmagnet being directly mounted to an inner wall of the rotor coveradjacent to the flange and including neodymium, and a coating layercoated on the upper surface of the stator except under the holdingmagnet, wherein, the holding magnet is positioned above the bearing withhaving an inner diameter larger than an inner diameter of the bearingand smaller than an outer diameter of the bearing so that its magneticforce directly affects to the bearing, and is positioned above thestator with having an outer diameter larger than an inner diameter ofthe stator and smaller than an inner diameter of the coating layer sothat its magnetic force directly affects to the stator.

In this aspect, the holding magnet is mounted the rotor cover in such away as to be adjacent to the rotating shaft.

Further, an upper part and a lower part of the bearing contact therotating shaft, an upper portion of the stator protrudes upwardly fromthe holder so that a gap is formed between the upper portion of thestator and the upper part of the bearing, the holding magnet protrudesbelow the flange of the rotor cover to preventing oil from beingdischarged from the bearing the outside, and an outer diameter of thelower part of the bearing is smaller than an inner diameter of theholder.

Further, a middle part of the bearing has an inner circumferentialsurface that not contact the rotating shaft.

Further, a height of the bearing is equal to a height of the stator.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentinvention will be more clearly understood from the following detaileddescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a schematic sectional view showing a spindle motor, accordingto the preferred embodiment of the present invention; and

FIG. 2 is a schematic sectional view showing a conventional spindlemotor.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, a spindle motor, according to the preferred embodiment ofthe present invention, will be described in detail with reference to theaccompanying drawing.

As shown in FIG. 1, a spindle motor 100 includes a rotary unit 101 and astationary unit 105.

The rotary unit 101 is the rotating part of the motor 100, and isprovided with a rotating shaft 111, a rotor cover 121, a magnet 131, anda holding magnet 141.

The rotating shaft 111 rotates a turntable (not shown).

The rotor cover 121 serves to rotate the rotating shaft 111, with ashaft fitting hole 122 formed in the center of the rotor cover 121 forfitting the rotating shaft 111 into the shaft fitting hole 122. And, therotor cover 121 is secured to the rotating shaft 111 by flange 142.Further, the rotor cover 121 extends in a circumferential direction, andan edge of the rotor cover 121 is bent downwards to cover a stator 135.

The magnet 131 forms a magnetic field, and is secured to an inner wall123 which is provided on the downwardly bent edge of the rotor cover121.

The holding magnet 141 is mounted to the inner surface of the rotorcover 121 so as to prevent a disk from being damaged when the disk isrotated. Unlike the prior art, the holding magnet 141 is directlymounted to the rotor cover 121 adjacent to the flange 142 without usinga back yoke, and is installed adjacent to the rotating shaft 111. And,the holding magnet 141 has a rectangular cross section positioned abovea bearing 115. Further, in order to prevent oil from being dischargedfrom the bearing 115 to the outside when the rotating shaft 111 isrotated, the holding magnet 141 is installed adjacent to the bearing115.

The holding magnet 141 is positioned above the bearing 115 with havingan inner diameter larger than an inner diameter of the bearing 115 andsmaller than an outer diameter of the bearing 115 so that its magneticforce directly affects to the bearing 115, and is positioned above thestator 135 with having an outer diameter larger than an inner diameterof the stator 135 and smaller than an inner diameter of the coatinglayer 143 so that its magnetic force directly affects to the stator 135.

The holding magnet 141 includes neodymium (Nd) in order to enhance themagnetic force. The stationary unit 105 is the fixed part of the motor100, which is not rotated, and is provided with the bearing 115, aholder 125, the stator 135, the coating layer 143, and a base 145.

The bearing 115 rotatably supports the rotating shaft 111. A height ofthe bearing 115 is equal to a height of the stator 135.

The holder 125 holds the bearing 115 to secure the bearing 115 to apredetermined position. The bearing 115 is firmly coupled to the innercircumferential surface of the holder 125.

The stator 135 forms an electric field when external power is applied tothe stator 135. The stator 135 has a bobbin 136 which is secured to theouter circumferential surface of the holder 125, and a coil 137 which iswound on the bobbin 136.

Meanwhile, an upper part and a lower part of the bearing 115 contact therotating shaft 111, an upper portion of the stator protrudes upwardlyfrom the holder 125 so that a gap is formed between the upper portion ofthe stator 135 and the upper part of the bearing 115, the holding magnet141 protrudes below the flange 142 of the rotor cover 121 to preventingoil from being discharged from the bearing 115 the outside, and an outerdiameter of the lower part of the bearing 115 is smaller than an innerdiameter of the holder 125. Further, a middle part of the bearing 115has an inner circumferential surface that not contact the rotating shaft111.

The coating layer 143 is coated on the upper surface of the stator 135to protect the stator 135. But, the coating layer 143 is made of thematerial not affected by the magnetic force. Therefore, the coatinglayer 143 isn't coated under the holding magnet 141 so that the holdingmagnet's magnetic force directly affects to the stator 135.

The base 145 functions to hold the entire motor 100. The central portionof the base 145 is bored and an edge of the bored portion protrudesoutwards, thus forming an insertion hole 146. A printed circuit board147 is mounted on the upper surface of the base 145, and controls asignal for driving the motor 100.

Although the preferred embodiment of the present invention has beendisclosed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the inventionas disclosed in the accompanying claims.

As described above, the present invention provides a spindle motor, inwhich a holding magnet is directly mounted to a rotor cover, unlike theprior art, in which the holding magnet is mounted to a stator via a backyoke, and in which the holding magnet is installed adjacent to the upperportion of a bearing, unlike the prior art, in which an oil dischargepreventing piece is installed to prevent oil from being discharged fromthe bearing, thus reducing the number of parts and increasing the yieldrate.

1. A spindle motor, comprising: a rotating shaft; a rotor cover securedto the rotating shaft by a flange, and rotating the rotating shaft; abearing rotatably supporting the rotating shaft; a holder to hold thebearing; a stator forming an electric field, coupled to the outercircumferential surface of the holder; a holding magnet having arectangular cross section positioned above the bearing, the holdingmagnet being directly mounted to an inner wall of the rotor coveradjacent to the flange and including neodymium; and a coating layercoated on the upper surface of the stator except under the holdingmagnet, wherein, the holding magnet is positioned above the bearing andhas an inner diameter larger than an inner diameter of the bearing andsmaller than an outer diameter of the bearing so that its magnetic forcedirectly affects the bearing, and is positioned above the stator and hasan outer diameter larger than an inner diameter of the stator andsmaller than an inner diameter of the coating layer so that its magneticforce directly affects the stator.
 2. The spindle motor as set forth inclaim 1, wherein the holding magnet is mounted to the rotor cover insuch a way as to be adjacent to the rotating shaft.
 3. The spindle motoras set forth in claim 1, wherein an upper part and a lower part of thebearing contact the rotating shaft, an upper portion of the statorprotrudes upwardly from the holder so that a gap is formed between theupper portion of the stator and the upper part of the bearing, theholding magnet protrudes below the flange of the rotor cover to preventoil from being discharged from the bearing the outside, and an outerdiameter of the lower part of the bearing is smaller than an innerdiameter of the holder.
 4. The spindle motor as set forth in claim 1,wherein a middle part of the bearing has an inner circumferentialsurface that does not contact the rotating shaft.
 5. The spindle motoras set forth in claim 1, a height of the bearing is equal to a height ofthe stator.